Pt 56, S2, Q19 - None of the students taking literature are

by **bbirdwell** Mon Nov 09, 2009 11:39 am

Question Type: Inference

This argument is best worked by symbolizing the statements. From the first sentence, we get L --> -P (contrapositive P --> -L).

Next, we learn that some P = A.

Finally, R --> -P and thus (P --> -R).

We can (and should) "connect the dots" with these statements, building chains of inferences. We should begin by focusing on the element that appears most often (P). Thus:

P --> -L AND _R. Add the fact that "some P = A" and we can infer that some A --> (-L AND _R)

We must be able to prove the correct answer choice based on these facts. Answer choice (A) states that "Some A = _L." Can we prove this? Yes! Since "some A --> (_ L and _R)," some students taking Art (those who are also taking Physics) definitely are not taking Literature.

(B) says L --> -A, which we cannot prove with the facts given.
(C) says Some R --> -L. It’s possible, yes. But we cannot prove that is definitely happening.
(D) says R --> -L, and thus is also possible, but not certain.
(E) says Some A --> L. Again, this possibility is not ruled out by the facts given, but it is not supported, either. The correct answer must be definite, not merely possible.